Tire inflating systems in motor vehicles render it possible to change the tire pressure of tires on wheels of the vehicle from inside the vehicle even when the vehicle is moving. As a consequence, the tire pressure can be adjusted such that the road resistance of the tires, the wear and tear on the tires and the drive energy necessary to drive the vehicle are minimized on any road surface and/or in any loaded state of the vehicle. As a consequence, the service life of the tires is increased and the fuel consumption of the vehicle is reduced. All in all, the use of a tire inflating system consequently reduces the running costs for the vehicle.
A tire pressure regulation system and/or a tire inflating system is disclosed in DE 199 50 191 C1, in which one, two or also several lines can be fed through the rotary feedthrough in the wheel hub. The rotary feedthrough comprises at least one chamber that is delimited by one annular body arranged on the stator side and by one annular body arranged on the rotor side in a concentric manner with respect to the axis of rotation of the wheel. The chamber is in particular an annular chamber.
The stator-side annular body and/or stator and the rotor-side annular body and/or rotor are spaced from one another by a movement gap. If compressed air is to be transferred from the stator to the rotor and as a consequence to the wheel, the movement gap must be sealed on both sides of the chamber. This sealed arrangement is achieved by seals and/or sealing rings that can be activated pneumatically and/or can be controlled by way of a control line. If the pressure in the tires is to be changed, the seal is initially activated by way of the control line. Then, in a second step, the pressure in the tires is changed by way of the rotary feedthrough. After venting the chamber by the rotary feedthrough, it is necessary to vent the control line in order to deactivate the seal, so that the seal does not suffer any unnecessary wear and tear as a result of friction of the rotor, which is rotating with respect to the stator and also with respect to the seal.
One disadvantage of the known tire pressure regulation system in accordance with DE 199 50 191 C1 is that, in addition to the line that is fed through the rotary feedthrough, an additional control line is fed to the wheel hub and/or to the rotary feedthrough, for which it is necessary to control an additional control pressure in order to switch the seal. The control and provision of a pressure of this type is generally achieved in a laborious manner by means of electromagnetically controlled valves.
A rotary feedthrough for a medium that can be fed through under pressure is disclosed in DE 10 2007 027 147 A1, in which this medium, in particular compressed air, is likewise transferred from a stator to a rotor. A seal is pressed against the rotor by means of the pressure of the compressed air that is fed through the rotary feedthrough from the stator, thus bridging a gap. As a consequence, the seal lies on the rotor in the case of compressed air being fed through the rotary feedthrough, whereas if compressed air is not fed through, the seal lies free. However, compressed air can escape through the gap between the stator and the rotor if the pressure of this compressed air is not sufficient to press a piston against a seal to such an extent that this seal reshapes and lies against the rotor. This can be the case for a short time period during the build-up and release of pressure.